Optical disk recorders use an objective lens to focus a laser beam onto a record medium and for transmitting a reflected laser beam from the medium to the detector apparatus for use in controlling the focusing, track seeking and following and data readback for the optical disk player. Such objective lens supports have taken various shapes, forms, and designs. These supports enable the laser beam to be tracked along a record track of a disk or plate medium as well as for moving the beam from one track to an adjacent track. Axial motion of the actuator is used for focusing control. An important aspect of any of these actuators is that they exhibit a sufficiently high resonant frequency such that parasitic vibrations do not interfere with either the focusing or the so-called track following or seeking operations.
The present invention concerns an objective lens holder which provides the track following and seeking functions through rotary motions and the focusing control through actual motions. This general type of objective lens holder is known in the art. For example: in Tsurushima et al., U.S. Pat. No. 4,482,988 shows such an actuator wherein an objective lens is supported on a radially extending beam which is rotatable about an axis and is axially movable parallel to such axis. This patent also shows a tubular cylinder supporting an objective lens having a slightly different arrangement wherein the support is a series of concentric cylinders with the objective lens being off center from the center of rotation of the cylinder. It is desired to provide a higher performance objective lens support not shown in this reference by reducing the inertia of the actuator i.e., reducing the mass at a radially extremity from the center of rotation.
Kasahara et al., in U.S. Pat. No. 4,679,903 shows such a rotary objective lens support having a peripheral vibration damper. It is desired to provide vibration elimination without increasing the inertia of rotation of the objective lens support. The objective lens support shown in this reference includes a cup-shaped cylinder with radially extending arms for supporting an objective lens. It is desired to provide a simpler support which is moldable and yet provides high resonant frequency for high performance operations.
Musha in U.S. Pat. No. 4,715,024 shows a rotary axially-moveable objective lens support in which the objective lens is mounted on a radially extending arm which results in an imbalance in the rotation i.e., all of the inertia is on one radius of the objective lens support; it is desired to provide a balanced lens support holder which is of simple construction.
Gijzen et al., in U.S. Pat. No. 4,767,187 shows a balance objective lens support of the rotary type which is also axially slidable. The balancing is achieved through a complex construction which is desired to be avoided.
Nanno et al., U.S. Pat. No. 4,790,628 shows a rotary objective lens support in which the lens is mounted on an extending radially arm. FIG. 9 of this reference shows a gain and phase chart wherein no vibrations are induced into the rotary lens support up to 10,000 Hertz. It is noted that the center support is a relatively large cylinder which adds to the rotational inertia of the objective lens holder. It is desired to provide a more compact objective lens holder which will facilitate higher frequencies of operation such as above 20,000 Hertz.
Ozaki et al., in U.S. Pat. No. 4,796,248 shows another cylindrical actuator wherein the objective lens is mounted offset from the center of rotation of the cylindrical or tubular assembly. Pan Sluys et al., in US Patent 4,817,076 shows another actuator having a large number of products in the assembly which is desired to be avoided.
Japan published unexamined patent application 60-38738 is another showing of the actuator of Musha et al. supra.